Java StringBuffer codePointCount()用法及代码示例

StringBuffer类的codePointCount()方法用于将BeginBuffer到StringBuffer所包含的String的endIndex指定范围内的Unicode代码点数返回。此方法将beginIndex和endIndex作为参数，其中beginIndex是文本范围的第一个字符的索引，endIndex是文本范围的最后一个字符的索引。索引引用char值(Unicode代码单位)，并且索引的值必须介于0到length-1之间。范围从beginIndex开始，在索引endIndex – 1处的字符结束。因此，文本范围的长度(以字符为单位)为endIndex-beginIndex。

用法:

public int codePointCount(int beginIndex,
                               int endIndex)

参数：此方法有两个参数：

beginIndex：int值，表示文本范围的第一个字符的索引。
endIndex：int值，表示文本范围的最后一个字符之后的索引。

返回值：此方法返回int值，该值表示指定文本范围内的Unicode代码点的数量。

异常：在以下情况下，此方法将引发IndexOutOfBoundsException：

beginIndex小于零，
或endIndex大于String的长度，
或beginIndex大于endIndex。

以下示例程序旨在说明StringBuffer.codePointCount()方法：

示例1:

// Java program to demonstrate 
// the codePointCount() Method. 
  
class GFG { 
    public static void main(String[] args) 
    { 
  
        // create a StringBuffer object 
        // with a String pass as parameter 
        StringBuffer 
            str 
            = new StringBuffer("Welcome to GeeksforGeeks"); 
  
        // print string 
        System.out.println("String = " + str.toString()); 
  
        // returns the codepoint count from index 4 to 10 
        int codepoints = str.codePointCount(4, 10); 
  
        System.out.println("No of Unicode code points "
                           + " between index 4 and index 10 = "
                           + +codepoints); 
    } 
}

输出：

String = Welcome to GeeksforGeeks
No of Unicode code points  between index 4 and index 10 = 6

示例2:

// Java program to demonstrate 
// the codePointCount() Method. 
  
class GFG { 
    public static void main(String[] args) 
    { 
  
        // create a StringBuffer object 
        // with a String pass as parameter 
        StringBuffer 
            str 
            = new StringBuffer("GeeksForGeeks contribute"); 
  
        // print string 
        System.out.println("String = "
                           + str.toString()); 
  
        // returns the codepoint count 
        // from index 3 to 7 
        int
            codepoints 
            = str.codePointCount(13, 17); 
  
        System.out.println("No of Unicode code points"
                           + " between index 13 and 17 = "
                           + codepoints); 
    } 
}

输出：

String = GeeksForGeeks contribute
No of Unicode code points between index 13 and 17 = 4

示例3:演示IndexOutOfBoundsException

// Java program to demonstrate 
// exception thrown by the codePointCount() Method. 
  
class GFG { 
    public static void main(String[] args) 
    { 
  
        // create a StringBuffer object 
        // with a String pass as parameter 
        StringBuffer 
            str 
            = new StringBuffer("GeeksForGeeks"); 
  
        try { 
  
            // make beginIndex greater than endIndex 
            int codepoints = str.codePointCount(2, 0); 
        } 
  
        catch (Exception e) { 
            System.out.println("Exception: " + e); 
        } 
    } 
}

输出：

Exception: java.lang.IndexOutOfBoundsException

参考文献：
https://docs.oracle.com/javase/10/docs/api/java/lang/StringBuffer.html#codePointCount(int, int)

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注：本文由纯净天空筛选整理自AmanSingh2210大神的英文原创作品 StringBuffer codePointCount() method in Java with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。